TWI544225B - Motor control system with electrical insulation deterioration detecting device and method of detecting electrical insulation deterioration of motor - Google Patents

Description

Motor control device with insulation degradation detecting device and insulation degradation detecting method for motor

The present invention relates to a motor control device including an insulation degradation detecting device that detects insulation degradation of an electric motor (abnormally reduced insulation resistance), and a method of detecting insulation degradation of the motor.

The servo motor is driven by a motor control device including a PWM controlled inverter circuit. Among the work machines, the work machine that uses the cutting fluid for machining may have the cutting fluid attached to the motor. Depending on the nature of the cutting fluid, the cutting fluid flows into the interior of the motor, which may cause problems in the electrical insulation of the motor. The electrical insulation degradation of the motor will gradually deteriorate, eventually leading to grounding. Once the motor is grounded, the leakage circuit breaker will trip, the motor control device will be broken, and the system using the motor will be shut down. System downtime can have a huge impact on the plant's production line. Therefore, from the viewpoint of prevention of preservation, it is necessary to have a device capable of detecting insulation deterioration of the motor.

As a conventional method for detecting insulation degradation of a motor, there are:

(1) Method of using an electrical insulation resistance meter

(2) Inserting a series circuit of a capacitor and a resistor between the poles of either or both of the pair of DC input portions (ie, the positive electrode and the negative electrode) of the PWM-controlled inverter circuit and the ground (ground), A method of detecting a potential difference between two ends of a resistor of the series circuit to detect insulation degradation of the motor without stopping the driving of the motor (Patent Document 1)

(3) Grounding the DC input portion of the PWM-controlled inverter circuit (connected to the ground), applying a DC voltage applied to the inverter device to the motor using the semiconductor element included in the inverter circuit, and measuring this Method for obtaining electric insulation resistance of a motor by DC voltage and DC current of the inverter device (Patent Document 2)

(4) Insert a resistor and a switch between the negative pole of the PWM inverter connected to the power supply through the circuit breaker and the ground. When the circuit breaker is open, turn off the switch to make the positive electrode of the PWM inverter The switch is in an on state, and a method of reducing the voltage of the resistor (Patent Document 3) is obtained.

[Previous Technical Literature]

[Patent Literature]

[Patent Document 1] Japanese Patent Laid-Open Publication No. 2005-201669

[Patent Document 2] Japanese Patent Laid-Open No. Hei 6-94762

[Patent Document 3] Japanese Laid-Open Patent Publication No. 2009-204600

In the above (1) method using an insulation resistance meter, the wiring between the motor and the motor control device is removed, and an insulation resistance meter is connected between the coil of the motor and the ground (ground), and the electrical insulation resistance is measured, according to the electrical property. The value of the insulation resistance is used to detect insulation degradation. However, this method has to remove the wiring of the motor and requires a lot of man-hours, which is a problem.

In the method of (2) above, the leakage current flowing through the power source causes The current flowing through the detection circuit is affected, causing an error in the detection of insulation degradation, which is a problem.

In the method of the above (3), the DC side of the inverter circuit is grounded (connected to the ground), and the DC voltage of the inverter device is applied to the motor by the semiconductor element in the inverter circuit. Next, the DC input voltage and the DC input current of the inverter circuit at this time are measured, and the electrical insulation resistance of the motor is obtained. However, in this method, when the electrical insulation of the motor deteriorates and the grounding occurs, the DC voltage of the inverter circuit is short-circuited due to the conduction of the semiconductor element in the inverter circuit. As a result, there is a problem that the semiconductor element is broken. Further, in the detector for measuring the direct current, a small current flows during the detection of the insulation degradation, and a large current flows normally when the motor is controlled. Therefore, it is necessary to flow a large current and accurately detect a small current current detector. However, the general current detector cannot obtain such accuracy, and there is a problem in improving the detection accuracy.

In the method of (4), when a capacitor is provided between the DC portion of the PWM inverter and the ground to combat noise, it takes time to stabilize the voltage of the insulation resistance detecting resistor by the capacitor. The switching power supply of the positive pole of the inverter circuit is not problematic in the inverter circuit that can open the semiconductor switch at all times. However, if the semiconductor switching power supply of the positive pole of the inverter circuit is as shown in FIG. 5, when the upper part of the inverter circuit is mounted on the capacitor and the diode for the bootstrap circuit, the positive power supply is only in the short time of the PWM operation. The inside can be turned on, so before the insulation resistance is detected, the semiconductor switch of the positive electrode is turned off, resulting in failure to use, which is a problem. In addition, the circuit of FIG. 5 is a self-excited inverter circuit, and the transistor TR1 constituting the semiconductor switch is TR6, its driving signal (gate signal) is given from the driving circuits DC1~DC6 respectively set for the transistor signals TR1 to TR6.

The present invention has been made in order to solve the above problems, and an object of the invention is to provide a motor control device having an insulation resistance detecting function, which does not need to disassemble a wiring of a motor, and even if the motor is grounded, the semiconductor switch of the inverter circuit is not damaged, and The bootstrap circuit is applied to the drive circuit of the semiconductor switch and is not affected by the leakage current from the power supply.

Another object of the present invention is to provide a method for detecting insulation degradation of an electric motor, which is not affected by leakage current generated by switching of the inverter circuit, and does not cause a semiconductor switch in the inverter circuit even if the motor is grounded. In the case of damage, the insulation deterioration of the motor can be accurately detected.

A motor control device including an insulation degradation detecting device according to the present invention includes a rectifier circuit, an inverter circuit, and an insulation degradation detecting device. The rectifier circuit is connected to the AC power supply via a circuit breaker, and a smoothing capacitor is provided between the positive DC output portion and the negative DC output portion. Further, one or more inverter circuits are constituted by a pair of semiconductor switches connected in series, and a connection point of a pair of semiconductor switches is a plurality of arm circuits of an AC output portion, which are formed by parallel connection, and the upper part of the plurality of arm circuits The drive circuit of the semiconductor switch is composed of a bootstrap circuit, and a voltage is applied to the excitation coil of the complex phase of one or more motors. The insulation deterioration detecting means detects the insulation resistance of the motor driven by the inverter circuit to detect deterioration of the insulation resistance.

In the present invention, an insulation degradation detecting device including a voltage dividing circuit, a detecting operation control unit, and an insulation resistance detecting unit is used. The voltage dividing circuit is disposed such that one of the positive DC output portion and the negative DC output portion is separated from the ground by a normally open switching circuit. The detection operation control unit sets the normally open switch circuit to a closed state while the circuit breaker is in the open state. Further, the detection operation control unit drives the same operation than the reverse operation, and applies a positive voltage and a negative voltage to the excitation coil of at least one phase from the smoothing capacitor, and performs a detection operation; the drive is at least in the complex arm circuit. In one arm circuit, one of the pair of semiconductor switches is in an open state, and the other is in an off state, and then one of the pair of semiconductor switches is turned off and the other is turned on; and the detecting operation is performed by the semiconductor switch in the lower stage. During this period, the bootstrap circuit of the semiconductor switch of the upper stage is brought into a charging operation state. Next, in the detection operation, the insulation resistance detecting unit detects the insulation resistance based on the divided voltage output from the voltage dividing circuit and the DC voltage input to the inverter circuit. Here, the "reverse detection operation using the same duty ratio PWM signal" refers to driving with a PWM signal having a certain pulse width, which is a pair of semiconductor switches in at least one arm circuit of the object (the semiconductor of the upper stage) One of the switch and the semiconductor switch of the lower stage is in an open state, and the other is in an off state, and then one of the switches is turned off and the other is turned on.

According to the present invention, by performing such a detection operation, the semiconductor switch used in the upper stage of the inverter circuit and the semiconductor switch in the lower stage are driven without rotating the motor, and a voltage is applied to the exciting coil, so that the insulation resistance can be reliably detected. . In addition, when the semiconductor switch of the lower stage is in the open state, The bootstrap circuit of the semiconductor switch of the upper stage is in a charging operation state, so that the bootstrap circuit can be used in the driving circuit of the semiconductor switch of the upper stage.

In addition, when detecting the motor with reduced insulation resistance, when determining which excitation coil is the cause of the insulation resistance, the plurality of arm circuits are sequentially selected to make one pair of semiconductor switches included in each arm circuit. Detection action. By doing so, it is possible to find out which phase of the exciting coil causes the insulation resistance to become small.

According to the present invention, the general operation of the motor is stopped, and the circuit breaker is switched OFF to cut off the AC power source to detect the insulation resistance of the motor. Therefore, in the detection of the insulation resistance, it is not affected by the leakage current flowing through the power supply line or the power supply noise. In addition, since the insulation resistance is detected by using the divided voltage output from the voltage divider circuit that is energized only when the insulation resistance is detected, the resistor for detecting the insulation resistance of the voltage divider circuit can be made into a dedicated resistor. value. In the case of the insulation deterioration detection, the voltage divider circuit becomes a resistance load for the motor and the smoothing capacitor. Therefore, even if the motor side is grounded, the overcurrent does not pass through the smoothing capacitor and flows through in a short time. Semiconductor switch. Therefore, even when the motor is grounded, the semiconductor switch in the inverter circuit can be prevented from being damaged. Further, the control power source required for operating the insulation degradation detecting device may be separately prepared without using a power source connected to the circuit breaker, or may be connected to a power source circuit connected to the power source without passing through the circuit breaker. In addition, it is not necessary to disassemble the wiring of the motor in order to detect the insulation resistance, and no special man-hours are required.

In particular, according to the present invention, the voltage dividing circuit can be electrically connected to the other end of the first resistor electrically connected to the negative DC output portion, and the other end of the second resistor electrically connected to the ground portion at one end is electrically connected to each other. Connected to form a person. In this case, it is preferable that the voltage across the first resistor is input to the insulation resistance detecting portion as the divided voltage V _R1 , and the second resistor serves as protection against overcurrent when the motor is in the grounded state. resistance. In this way, when the motor is grounded, it is possible to surely prevent overcurrent from occurring. Further, it is preferable that a normally-on switching circuit is disposed between the other end of the first resistor and the other end of the second resistor. In addition, a normally open switching circuit can also be placed between the second resistor and ground.

The insulation resistance detecting unit receives the divided voltage V _R1 and the inter-terminal voltage V _{DC of the} smoothing capacitor, and the duty ratio is D%, the resistance value of the first resistor is R ₁ , and the resistance value of the second resistor is R. _{In the case of 2} , the insulation resistance R _M can be obtained by an arithmetic expression of R _M =V _DC ×(D/100)×(R ₁ /V _R1 )−(R ₁ +R ₂ ). By using this equation, the insulation resistance can be obtained without removing the motor from the device.

When the inverter circuit is two or more inverter circuits provided for two or more motors, the detection operation control unit can be configured as follows. In other words, the detection operation control unit may be configured to select one inverter circuit to be detected from the complex inverter circuit, and perform a detection operation in the selected one inverter circuit. In this way, the insulation resistance of two or more motors can be detected by one voltage dividing circuit and one insulation resistance detecting unit.

In the case where the inverter circuit is three or more inverter circuits provided for three or more motors, the detection operation control unit can be configured to perform the following operations. That is to say, a combination of a plurality of inverter circuits is determined from three or more inverter circuits, and two inverter circuits corresponding to the determined complex combination are respectively selected, and the selected two reverse circuits are selected. The detector circuit simultaneously performs a detection operation. In this case, two inverter circuits are identified based on the parallel insulation resistance detected by the insulation resistance detecting portion, and the two inverter circuits include an inverter circuit for driving a motor having a reduced insulation resistance. Then, the two inverter circuits identified in the detection operation are respectively performed. After the detection operation control unit performs the above operation, the insulation resistance detecting unit may ascertain the motor having a reduced insulation resistance based on the detected insulation resistance.

In the method for detecting insulation deterioration of the motor of the present invention, the circuit breaker is initially placed in an open state. Thereafter, a voltage dividing circuit is electrically connected between one of the positive DC output portion and the negative DC output portion and the ground. Driving with the same operation repeatedly than the PWM signal, applying a positive voltage and a negative voltage to the excitation coil of at least one phase from the smoothing capacitor, and simultaneously performing a detecting operation; the driving is in at least one arm circuit of the plurality of arm circuits, One of the pair of semiconductor switches is turned on, and the other is turned off, and then one of the semiconductor switches is turned off and the other is turned on; the detecting operation is to make the semiconductor of the upper stage during the opening of the semiconductor switch in the lower stage The bootstrap circuit of the switch becomes the charging action state. Next, the insulation resistance of the motor is detected based on the divided voltage output from the voltage dividing circuit and the DC voltage input to the inverter circuit.

When the inverter circuit is two or more inverter circuits provided for two or more motors, one inverter circuit to be detected is selected from two or more inverter circuits. . Then, by performing a detection operation in the selected inverter circuit, it is possible to detect deterioration of insulation resistance of two or more motors.

When the inverter circuit is three or more inverter circuits provided for three or more motors, a combination of a plurality of inverter circuits is determined from three or more inverter circuits. Next, two inverter circuits corresponding to the determined complex combination are respectively selected, and in the selected two inverter circuits, the detection operation is simultaneously performed to detect the parallel insulation resistance. Next, two inverter circuits are identified, which include an inverter circuit for driving a motor with reduced insulation resistance. Thereafter, the two inverter circuits are inspected for detection, and the motor with reduced insulation resistance is ascertained based on the detected insulation resistance.

Embodiments of a motor control device including an insulation deterioration detecting device and an insulation deterioration detecting method for an electric motor according to the present invention will be described in detail with reference to the following drawings. Fig. 1(A) is a schematic diagram showing a configuration example of a motor control device 1 for driving one three-phase AC motor (motor) M by one inverter circuit 5, and (B) for electric power of a semiconductor switch constituting the upper stage which will be described later. An illustration of a bootstrap circuit used by the crystals TR1 to TR3. The motor control device 1 is connected to the three-phase AC power source AC through an electromagnetic contactor as the circuit breaker 2. The motor control device 1 will output from a three-phase AC power source AC The three-phase AC is full-wave rectified by a full-wave rectifying circuit 3 constructed by connecting six diodes D1 to D6 bridges to obtain a DC voltage. Then, the DC voltage is smoothed by a smoothing capacitor C composed of an electrolytic capacitor. In the present embodiment, the full-wave rectifying circuit 3 and the smoothing capacitor C constitute a rectifying circuit. The both ends of the smoothing capacitor C constitute a positive DC output portion 4A and a negative DC output portion 4B.

Further, the inverter circuit 5 is constituted by a bridge circuit formed by connecting three arm circuits 51 to 53 in parallel. Each of the three arm circuits 51 to 53 is constituted by one of transistors, and the semiconductor switches (TR1 and TR4, TR2 and TR5, TR3 and TR6) are connected in series. The connection points CP1 to CP3 of a pair of semiconductor switches (TR1 and TR4, TR2 and TR5, TR3 and TR6) are used as an AC output unit. Three-phase excitation coils W1 to W2 connected by a star in the motor M are connected to the connection points CP1 to CP3. In Fig. 1, between the neutral point of the star-connected three-phase excitation coils W1 to W2 and the ground (ground), there is an electrical insulation resistance RM, which is gradually deteriorated due to the deterioration of the electrical insulation of the motor. Become smaller. The diodes D are connected in anti-parallel to the six transistors TR1 to TR6 used in the inverter circuit 5, respectively. In the present embodiment, the inverter circuit 5 is subjected to PWM control in accordance with a PWM control signal output from a PWM control circuit 10 (not shown) including an inverter control circuit, and converts DC power into AC power for output. The PWM control circuit 10 detects the rotor position of the motor M based on the output of the position detector such as an encoder (not shown) fixed to the output shaft of the motor M, and performs the position of the rotor of the motor M based on the detection information. Or speed control. Further, as shown in FIG. 1(B), the transistors TR1 to TR3 in the upper stage are respectively provided with a resistor R ₀ , a capacitor C ₀ , a diode D _{0 ,} and a DC power source DPS. Bootstrap circuit BSC. Further, on the bases of the transistors TR1 and TR4, drive circuits DC1 and DC4 for applying PWM signals to the transistors are disposed. On the transistors TR2 and TR5, and on the transistors TR3 and TR6, a bootstrap circuit and a drive circuit as shown in Fig. 1(B) are also disposed. The bootstrap circuit BSC during the lower segment of the transistor TR4 is turned on, with the current flowing through the DC power source DPS → resistive R ₀ → diode D ₀ → capacitor C ₀ → electrically TR4 circuit of the crystal, the capacitor C ₀ is charged . The results, with the charge of the capacitor C _0, the transistor TR1 can base - emitter voltage rise between. Therefore, as will be described later, even after the circuit breaker 2 is turned on, by turning on the PWM driving signal via the driving circuit DC1 at the base of the upper transistors TR1 to TR3, the conduction state of the upper transistors TR1 to TR3 can be ensured. .

The motor control device 1 incorporates an insulation degradation detecting device 6 that detects electrical insulation degradation (decrease in insulation resistance R _M ) of the motor M driven by the inverter circuit 5 . The insulation degradation detecting device 6 includes a voltage dividing circuit 7, a detecting operation control unit 8, and an insulation resistance detecting unit 9. The voltage dividing circuit 7 is disposed between one of the negative DC output portions 4B and the ground, and a normally open switching circuit SW composed of a relay contact is interposed therebetween. Specifically, the voltage dividing circuit 7 has a configuration in which the other end of the first resistor R1 which is electrically connected to the negative electrode DC output portion 4B at one end is electrically connected to the ground. Between the other ends of the second resistor R2, a normally open switch circuit SW that is always in an open state but is in a closed state after being input with a command is disposed. The voltage across the first resistor R1 is input to the AD converter in the voltage comparison unit 9 as a divided voltage. The second resistor R2 constitutes a protective resistor, and has a resistance value for preventing an overcurrent from flowing when the motor M is in a grounded state. The voltage dividing circuit 7 is configured as described above, and when the motor M is in the grounded state, it is possible to surely prevent the occurrence of an overcurrent.

The detection operation control unit 8 causes the normally open switch circuit SW to be in a closed state when the circuit breaker 2 including the electromagnetic contactor is in an open state. The detection operation control unit 8 performs the following detection operation. First, the same operation is used to drive the PWM signal repeatedly, and the driving is to make a pair of semiconductor switches in at least one of the three arm circuits 51 to 53 (hereinafter, the arm circuit 51 is exemplarily described as an example). (Representatively, the transistors TR1 and TR4 are exemplarily described below), one of them is in an open state, and the other is in an off state, and then one of them is in an off state and the other is in an on state. For example, an on/off operation is performed: during the period in which the transistor TR1 is turned on, the transistor TR4 is turned off, and during the period in which the transistor TR4 is turned on, the transistor TR1 is turned off. By this opening/closing operation, a positive voltage and a negative voltage are alternately applied from the smoothing capacitor C to the exciting coil W1 of one phase. Next, as aforesaid, with respect to the upper section so that the transistor TR1 of the BSC bootstrap circuit, the transistor TR4 were lower during the opening period, for charging the capacitor C ₀ of the charging operation.

The so-called "using the same work over the PWM signal to drive repeatedly", as illustrated in Figure 2 (A) to (C), refers to the use of PWM signals with the same duty ratio to drive repeatedly, the drive is used during PWM control The PWM signal used is a working ratio smaller than 100% (for example, 50%), and the pulse width is a certain PWM signal, so that one of the objects is open to one of the transistors TR1 and TR4, and the other is One party is in the off state, and then one of them is in the off state and the other is in the open state. As shown in the right diagram of Fig. 2, by using such a PWM signal, the average of the voltage applied to the exciting coil can be made into a voltage value in accordance with the duty. For example, when the duty ratio is 60%, the transistor TR1 is in an open state during 60% of operation (the transistor TR4 is in an off state during this period), and the transistor TR4 is in an open state during the remaining 40% of operation (the transistor during this period) TR1 is off). The duty ratio can be such that the bootstrap circuit can be brought into a charging operation state by the lower stage transistor, and the necessary voltage can be applied to the exciting coil in the detection of the insulation resistance R _M . That is, it is desirable to set the duty ratio upper limit value to the gate power supply of the transistors TR1 to TR3 on the upper side of the inverter circuit 5, for example, the bootstrap circuit shown in FIG. 2(B) The value of charging. The duty ratio is preferably set to a value that prevents the detection accuracy of the insulation resistance from being lowered even if the average voltage applied to the motor is lowered.

Next, in the detection operation, the insulation resistance detecting unit 9 detects the insulation resistance based on the divided voltage output from the voltage dividing circuit and the DC voltage input to the inverter circuit. The insulation resistance detecting unit 9 is composed of an analog-digital converter AD and a central processing unit CPU. The analog-to-digital converter AD converts the divided voltage V _R1 output from the voltage dividing circuit 7 and the DC voltage (the voltage between the terminals of the smoothing capacitor) V _DC input to the inverter circuit 5 into digital data. . On the other hand, the central processing unit CPU calculates the insulation resistance R _M based on the arithmetic expression described later.

The arithmetic expression used is determined as follows. First, the resistance value of the insulation resistance R _M of the motor M is R _M , the voltage between the terminals of the smoothing capacitor is V _DC , the voltage across the first resistor R1 is V _R1 , the duty ratio is D%, and the first resistance When the resistance value of the body R1 is R ₁ and the resistance value of the second resistor R2 is R ₂ , the voltage V _R1 across the first resistor _R1 can be expressed by the following equation.

V _R1 =V _DC ×(D/100)/(R _M +R ₁ +R ₂ )×R ₁

In addition, in this case, compared with the V _DC , the voltage drop of the inverter element is regarded as a small one and is ignored. The insulation resistance R _M can be calculated from an arithmetic expression of R _M =V _DC ×(D/100)×(R ₁ /V _R1 )−(R ₁ +R ₂ ).

The calculation of the above arithmetic expression is performed by the central processing unit CPU. Further, in the present embodiment, the central processing unit CPU monitors the detected insulation resistance, and when the insulation resistance reaches a predetermined value or more, an alarm is issued to the user who uses the motor control device. When the alarm occurs, the user replaces the motor with the insulation resistance reduced, preventing the motor from being grounded and the system shut down. Further, in the present embodiment, the transistors TR1 and TR4 and the like are driven by one of the arm circuits 51 to 53 to be PWM-driven to be turned on/off alternately. Specifically, the driving is repeated, and the driving is performed by applying a voltage to one of the exciting coils to one of the transistors TR1 and TR4, etc., and turning it on with a 50% duty PWM signal. The other side of the transistor is off; after that it makes another One of the transistors is turned on with a 50% duty PWM signal, and one of the transistors is off. Using a 50% duty PWM signal, the absolute values of the positive and negative voltages applied to the excitation coil will be equal, and the detection of the insulation resistance and the charging operation of the bootstrap circuit can be performed in a balanced manner.

In the present embodiment, after the application of the positive voltage to the excitation coil W1 through the transistor TR1 to detect the insulation resistance, the charging operation of the bootstrap circuit of the transistor TR1 is performed while the application of the negative voltage to the excitation coil W1 through the transistor TR4. . Next, after the exciting coil W2 is applied with a positive voltage through the transistor TR3 to detect the insulation resistance, a charging operation of the bootstrap circuit of the transistor TR3 is performed while a negative voltage is applied to the exciting coil W2 through the transistor TR6. Thereafter, after the exciting coil W3 is applied with a positive voltage through the transistor TR2 to detect the insulation resistance, a charging operation of the bootstrap circuit of the transistor TR2 is performed while a negative voltage is applied to the exciting coil W3 through the transistor TR5.

Further, the order in which the voltage applied to the exciting coil is specified by the detection operation control unit 8 is not limited to this embodiment. Further, the detection operation control unit 8 can simultaneously perform the same detection operation as described above for the plurality of excitation coils, apply a voltage to each of the excitation coils, and simultaneously detect the insulation resistance.

In the detection operation, when the PWM control circuit 10 receives the PWM signal generation command issued by the detection operation control unit 8 for performing the detection operation, it will apply to one of the pair of transistors in the designated arm. The driving circuit gives a PWM signal of a prescribed duty, and the other transistor driving circuit is given an inversed specification. The (duty) PWM signal.

In the above-described embodiment, the insulation resistance is obtained by calculation using the above-described calculation formula. However, when the insulation resistance is detected, the calculation formula is not limited, and the insulation resistance can be relatively detected by a comparator. For example, when the insulation resistance R _{M is} high, the divided voltage V _R1 becomes low, and when the insulation resistance R _{M is} low, the divided voltage V _R1 becomes high. Therefore, when the insulation resistance R _{M is} deteriorated to some extent, the voltage corresponding to the divided voltage V _R1 is used as the voltage reference voltage Vref, and the divided voltage V _{R1 is} compared with the voltage reference voltage Vref, thereby being able to The insulation resistance R _M is detected sexually.

Further, the rectifier circuit 3 may be a circuit that can regenerate power to the three-phase AC power source AC, such as a PWM converter. In this case, when the insulation degradation is detected, the PWM converter is stopped to detect the insulation degradation.

Further, the control power source and the DC power source DPS necessary for the operation of the insulation degradation detecting device 6 are not prepared separately from the three-phase AC power source AC to which the circuit breaker 2 is connected. Further, the control power source may be configured to be connected to the three-phase AC power source AC without passing through the circuit breaker 2.

Fig. 3 shows a circuit configuration of a second embodiment of the motor control device of the present invention. In the circuit configuration shown in FIG. 3, when the same components as those of the circuit configuration shown in FIG. 1 are encountered, the symbol numbers marked by the components shown in FIG. 1 are added with a numerical symbol of 100 or 200, and the detailed description is omitted. Description. In the embodiment of Fig. 3, two inverter circuits 105 and 205 are connected to the full-wave rectifier circuit 103. Two motors M1 and M2 are connected to the two inverter circuits 105 and 205, respectively. In this embodiment, The insulation resistance can be detected by one insulation degradation detecting device 106 for each of the two motors. In this embodiment, the detection operation control unit 108 of the insulation degradation detecting device 106 is configured to open the normally open switching circuit SW while the circuit breaker 102 is in the open state, and to operate from the two inverters. In the circuits 105 and 205, one inverter circuit to be detected is sequentially selected, and the above-described detection operation is performed on the exciting coil of the complex phase in the selected inverter circuit.

Specifically, for example, the detection operation control unit 108 first causes the upper electrodes of the pair of transistors (TR1 and TR4, TR2 and TR5, TR3, and TR6) included in the arms 151 to 153 of the inverter circuit 105 to be 50. % of working ratio was during the oN state, the detected electric motor M1 resistance insulation resistance RM1 of R & lt _M1; thereafter, so that the lower segment of the transistor to work 50% of the ratio during an open state of the form, for the upper section of the transistor of The charging action of the bootstrap circuit. Next, the detection operation control unit 108 stops giving the PWM signal to the transistor in the inverter circuit 105, so that the arms 251 to 253 of the inverter circuit 205 include one pair of transistors (TR1 and TR4, TR2, and TR5, The transistor of the upper stage of TR3 and TR6) detects the resistance R _M2 of the insulation resistance RM2 of the motor M2 during the 50% duty ratio, and thereafter, the lower stage transistor is at 50% duty ratio. During the on state, the charging operation of the bootstrap circuit of the transistor of the upper stage is performed.

In this way, after the insulation deterioration is detected by the detection of the insulation resistance of one motor, the same detection operation can be performed on the inverter circuit corresponding to the remaining one motor, and the plurality of motors can be sequentially processed. Perform insulation resistance detection to reduce cost and perform multiple motors Insulation degradation determination of insulation resistance detection.

Fig. 4 shows a circuit configuration of a third embodiment of the motor control device of the present invention. In the circuit configuration shown in FIG. 4, the same components as those constituting the circuit shown in FIG. 1 (excluding the inverter circuit) are used, and the symbol numbers marked by the components shown in FIG. Detailed explanations are omitted. In the embodiment of Fig. 4, four inverter circuits 105, 205, 305, and 405 are connected to the full-wave rectifier circuit 203. Four motors M1 to M4 are connected to the four inverter circuits 105 to 405, respectively. In the present embodiment, the insulation resistance can be detected by one insulation deterioration detecting device 206 for each of the four motors as in the embodiment of Fig. 3 . When one unit detects the insulation deterioration of the motor one by one, the detection operation control unit 208 of the insulation deterioration detecting device 206 turns the normally open switch circuit SW into a closed state while the circuit breaker 202 is in the open state, and then sets the four switches from the fourth state. In the inverter circuits 105 to 405, one inverter circuit to be detected is sequentially selected, and the same detection operation as in the embodiment of Fig. 1 is performed in the selected inverter circuit.

Specifically, the first detection resistor R _M1 of the insulation resistance RM1 motor M1 by inverter circuit 105 of the drive, then detects the insulation resistance of the resistor R RM2 motor M2 by the inverter circuit 205 drives the _M2, followed by detecting motor M3 by the inverter circuit 305 drives the insulation resistance of the resistor RM3 R _{M3, M4} to the final detection resistor R & lt RM4 insulation resistance of the motor M4 by the inverter circuit 405 of the drive.

It is also possible to configure the detection operation control unit 208 to simultaneously select a plurality of inverter circuits, as in the case of selecting one inverter circuit as described above. The insulation resistance of the plurality of motors is detected. For example, two inverter circuits 105 and 205 are selected from the four inverter circuits 105 to 405 as the first combination. Then, the insulation resistances of the motors M1 and M2 driven by the selected two inverter circuits 105 and 205 (first combination) are detected. Next, the remaining two inverter circuits 305 and 405 (second combination) are selected. Then, the insulation resistances of the motors M3 and M4 driven by the remaining two inverter circuits 305 and 405 (second combination) are detected. According to this embodiment, the selected two inverter circuits can be combined as one to sequentially detect the insulation degradation of the motor. As long as the number of inverter circuits selected each time is the same number, the configuration of the detection operation control unit 208 is simple. Further, when a plurality of inverter circuits are combined as one to perform a detection operation, it is possible to determine that insulation degradation has occurred in one of the motors in one of the combinations. However, in particular, there is no way to immediately determine which motor has been insulated and deteriorated. Therefore, it is necessary to individually detect the insulation resistance of the two inverter circuits of the motor that drives the insulation resistance degradation as in the first embodiment. The motor with insulation degradation can be used.

Further, when there are five inverter circuits, for example, and cannot be divided into the same number of combinations, the number of the selected inverter circuits is not fixed, but is changed. In other words, the detection operation may be performed on the first combination of the three inverter circuits, and then the detection operation may be performed on the second combination of the two inverter circuits.

In order to ascertain the motor in which the insulation resistance of the four motors M1 to M4 is lowered, a configuration shown by a broken line in FIG. 4 is used, and the calculation result is sent back to the detection operation control unit 208 by the central processing unit CPU. Next, detect the movement The control unit 208 appropriately selects two inverter circuits from the plurality of inverter circuits, and simultaneously performs detection operations by these inverter circuits. That is to say, the PWM signals of the aforementioned duty are given to a pair of transistors in one arm circuit for two inverter circuits, respectively. In this manner, the insulation resistance detecting unit 209 detects the insulation resistance (parallel insulation resistance) in a state where the insulation resistances of the two motors driven by the two inverter circuits are connected in parallel. The central processing unit CPU calculates the parallel insulation resistance, and returns information of the two inverter circuits whose parallel insulation resistance is larger than a predetermined reference value, and returns the information to the detection operation control unit 208. The detection operation control unit 208 that has obtained the information performs the detection operation individually for the two inverter circuits that have been identified. Then, the central processing unit CPU calculates the insulation resistance of the two motors to determine the deterioration of the insulation resistance. Specifically, first, the inverter circuits 105 and 205 perform the detection operation simultaneously, and the parallel insulation resistances of the motors M1 and M2 are detected, and the detection operations of the inverter circuits 105 and 205 are stopped. Next, the inverter circuits 305 and 405 perform the above-described detection operation, and after detecting the parallel insulation resistance of the motors M3 and M4, the detection operations of the inverter circuits 305 and 405 are stopped. Next, when the parallel insulation resistance of the motors M1 and M2 is low, the inverter circuit 105 performs a detection operation, detects the insulation resistance of the motor M1, and stops the detection operation of the inverter circuit 105. Next, the inverter circuit 205 performs a detection operation, detects the insulation resistance of the motor M2, and stops the detection operation of the inverter circuit 205. In the case where the motor M3 or M4 fails, the detecting operation is performed for the inverter circuit 305, and the insulation resistance of the motor M3 is checked. After the measurement, the detection operation of the inverter circuit 305 is stopped. Next, the inverter circuit 405 performs a detection operation, detects the insulation resistance of the motor M4, and stops the detection operation of the inverter circuit 405. Thereby, the insulation deterioration of the four motors can be efficiently detected by the one insulation resistance detecting unit 209.

In each of the above embodiments, the general operation of the motor is stopped, and the electromagnetic contactor is turned OFF to cut off the three-phase AC power supply, thereby detecting the insulation resistance of the motor. Therefore, it is not affected by leakage current or power supply noise flowing through the power line. Further, since the insulation resistance is detected by using a detection resistor that is energized only when the insulation resistance is detected, the insulation resistance detecting resistor can be made into a resistor having a dedicated resistance value. In addition, even if the motor is grounded, there is no excessive current flow due to the protective resistor. Moreover, according to each embodiment, it is not necessary to disassemble the wiring of the motor, and no special man-hours are required. Further, in the motor control device that drives the plurality of motors, it is only necessary to constitute one insulation resistance detecting unit for the plurality of motors, and it is possible to reduce the cost. Further, the insulation resistance of each motor can be detected by one insulation resistance detecting portion. In addition, by adjusting the combination, the faulty motor can be quickly found even in the case of several motors. In addition, it is also possible to distinguish which phase of the motor has deteriorated in insulation.

In the above three embodiments, the negative DC output portions 4B and 104B are connected to the voltage dividing resistor circuits 7 and 107 at the time of detecting the insulation resistance, but the positive DC output portions 4A and 104A are connected to the voltage dividing resistor circuits 7 and 107. can.

In the above embodiment, the motor is a three-phase exciting coil having a star connection. However, the present invention can of course be applied to the detection of the insulation resistance of a motor having a triangular-connected three-phase exciting coil.

[Possibility of industrial use]

According to the present invention, the semiconductor switch used in the upper stage of the inverter circuit and the semiconductor switch in the lower stage are alternately driven without rotating the motor to apply a voltage to the exciting coil, so that the insulation resistance can be surely detected. In addition, when the semiconductor switch of the lower stage is in the open state, the bootstrap circuit of the semiconductor switch of the upper stage is in the charging operation state, so that the bootstrap circuit can be used in the driving circuit of the semiconductor switch of the upper stage.

1‧‧‧Motor control unit

2,102,202‧‧‧Circuit breaker

3,103,203‧‧‧Full-wave rectifier circuit

4A, 104A, 204A‧‧‧ positive DC output

4B, 104B, 204B‧‧‧Negative DC output

5,105,205,305,405‧‧‧inverter circuit

6,106,206‧‧‧Insulation degradation detection device

7,107,207‧‧‧Voltage voltage dividing circuit

8,108,208‧‧‧Detection Action Control Department

9,109,209‧‧‧Insulation resistance detection department

10,110,210‧‧‧PWM control circuit

TR1~TR6‧‧‧Optoelectronics (semiconductor switch)

D‧‧‧ diode

C‧‧‧Smoothing capacitor

R1‧‧‧1st resistor

R2‧‧‧2nd resistor

SW‧‧‧Normally open switch circuit

Fig. 1 (A) is a schematic circuit diagram showing an example of an embodiment of a motor control device according to the present invention in which one motor is driven by one inverter circuit, and (B) is a schematic view showing an example of a bootstrap circuit used.

[Fig. 2] (A) to (C) are diagrams of PWM signals whose duty ratio is less than 100% and the pulse width is constant.

Fig. 3 is a schematic circuit diagram showing an example of a second embodiment of the motor control device of the present invention in which two motors are driven by two inverter circuits.

Fig. 4 is a schematic circuit diagram showing an example of a third embodiment of the motor control device of the present invention in which three motors are driven by three inverter circuits.

[Fig. 5] An illustration of a bootstrap circuit is used in a driving circuit for driving a semiconductor switch for an upper portion of an inverter circuit.

1‧‧‧Motor control unit

2‧‧‧Circuit breaker

3‧‧‧Full-wave rectifier circuit

4A‧‧‧Positive DC output

4B‧‧‧Negative DC output

5‧‧‧Inverter circuit

6‧‧‧Insulation degradation detection device

7‧‧‧Voltage divider circuit

8‧‧‧Detection Action Control Department

9‧‧‧Insulation resistance detection department

10‧‧‧PWM control circuit

51~53‧‧‧ Arm

TR1~TR6‧‧‧Optoelectronics (semiconductor switch)

M‧‧‧Motor

W1~W3‧‧‧Exciting coil

RM‧‧‧Insulation resistance

D‧‧‧ diode

C‧‧‧Smoothing capacitor

R1‧‧‧1st resistor

R2‧‧‧2nd resistor

SW‧‧‧Normally open switch circuit

Claims (6)

A motor control device comprising: a rectifier circuit connected to an AC power source through a circuit breaker; and a smoothing capacitor between a positive DC output portion and a negative DC output portion; and one or more inverter circuits a pair of semiconductor switches are connected in series, and a connection point of the pair of semiconductor switches is a plurality of arm circuits of the AC output portion, and is connected in parallel. The drive circuit of the semiconductor switch of the upper stage of the plurality of arm circuits is composed of a bootstrap circuit is configured to apply a voltage to an excitation coil of a plurality of motors, and an insulation degradation detecting device detects insulation degradation of the motor; and the insulation degradation detecting device includes a voltage divider circuit. One of the positive DC output portion and the negative DC output portion is disposed between the ground and the normally open switching circuit, and the detection operation control unit is driven repeatedly by using the PWM signal of the same duty ratio, and the smoothing capacitor is at least one phase. The aforementioned excitation coils alternately apply a positive voltage and a negative voltage, and simultaneously check The operation is to open the normally open switch circuit while the circuit breaker is in an open state, and to enable one of the pair of semiconductor switches in at least one of the plurality of arm circuits to be in an open state. The other side is in an off state, and then one of the states is turned off and the other is turned on; the detecting operation is that the bootstrap circuit of the semiconductor switch of the upper stage is charged during the opening period of the semiconductor switch in the lower stage And an insulation resistance detecting unit that detects the insulation resistance based on the divided voltage output from the voltage dividing circuit and the DC voltage input to the inverter circuit in the detecting operation; the voltage dividing voltage The circuit is configured such that one end is electrically connected to the other end of the first resistor of the negative DC output portion, and one end is electrically connected to the other end of the grounded second resistor, and is electrically connected to each other. The voltage across the resistor is input to the insulation resistance detecting unit as the divided voltage V _{R1 ,} and the second resistor is in front. In the case where the motor is in a grounded state, the insulation resistance detecting unit is configured to input the voltage V _DC between the voltage-dividing voltage V _R1 and the smoothing capacitor as the input, and the duty ratio is D%. When the resistance value of the first resistor is R ₁ and the resistance value of the _second resistor is R ₂ , the insulation resistance R _M is R _M =V _DC ×(D/100)×(R ₁ /V _R1 )- The equation of (R ₁ + R ₂ ) is obtained. The motor control device according to the first aspect of the invention, wherein the one or more inverter circuits are two or more inverter circuits provided for two or more motors, and the detection operation control unit is The inverter circuit as the detection target is selected from the plurality of inverter circuits, and the detection operation is performed in the selected one inverter circuit. The motor control device according to the first aspect of the invention, wherein the one or more inverter circuits are for three or more The inverter control circuit is provided in three or more inverter circuits, and the detection operation control unit is configured to determine a combination of the plurality of inverter circuits from the inverter circuits of the three or more inverters, and respectively select and correspond to The two inverter circuits that are combined in the determined plurality of combinations are simultaneously subjected to the detection operation described above for the selected two inverter circuits, and the parallel insulation resistance detected by the insulation resistance detecting unit at this time is used to ascertain The two inverter circuits including the inverter circuit that drives the motor having a reduced insulation resistance are further subjected to the detecting operation in the two inverter circuits that are ascertained, and the insulation resistance detecting unit is based on The plurality of the aforementioned insulation resistances are detected to ascertain the aforementioned motor having a reduced insulation resistance. An insulation deterioration detecting method for an electric motor is an insulation deterioration detecting method for detecting deterioration of electrical insulation resistance of one or more motors driven by a motor control device, the motor control device including: a rectifier circuit connected to the circuit breaker An AC power supply includes a smoothing capacitor between the positive DC output portion and the negative DC output portion; and one or more inverter circuits in which a pair of semiconductor switches are connected in series, and a connection point of the pair of semiconductor switches is an alternating current The plurality of arm circuits of the output unit are connected in parallel, and the drive circuit of the semiconductor switch of the upper stage of the plurality of arm circuits is constituted by a bootstrap circuit, and one or more motors (n is an integer of 1 or more) Applying a voltage to the excitation coil of the plurality of phases; the method for detecting insulation degradation of the motor is characterized in that: the circuit breaker is in an open state, and thereafter, the voltage divider circuit is electrically connected to the positive DC output portion and the negative DC Between one of the output units and the ground, the same operation is used to drive the PWM signal repeatedly. And applying a positive voltage and a negative voltage to the exciting coil of at least one phase from the smoothing capacitor, and performing a detecting operation; wherein the driving is performed on at least one of the pair of semiconductor switches of the plurality of arm circuits One of the parties is in an open state, and the other is in an off state, and then one of the parties is in an off state and the other is in an on state; the detecting operation is to perform the aforementioned bootstrap of the semiconductor switch of the upper stage during the opening of the semiconductor switch in the lower stage The circuit is in a charging operation state, and the voltage dividing circuit is configured such that one end is electrically connected to the other end of the first resistor of the negative DC output portion, and one end is electrically connected to the second resistor of the ground. One end is electrically connected to each other, and in the detecting operation, the insulation resistance is detected in accordance with the divided voltage output from the voltage dividing circuit and the DC voltage input to the inverter circuit. as the voltage across the resistor divided voltage V _R1, the divided voltage V _R1 and the smoothing capacitor Inter-terminal voltage V _DC, the working ratio of D%, the resistance value of the first resistor R _1, the resistance value of the second resistor R _2, the insulation resistance R _M lines by R _M = V _DC × The calculation formula of (D/100) × (R ₁ /V _R1 ) - (R ₁ + R ₂ ) is obtained, and the deterioration of the insulation resistance of the motor is detected based on the insulation resistance. The method of detecting an insulation deterioration of a motor according to the fourth aspect of the invention, wherein the one or more inverter circuits are two or more inverter circuits provided for two or more motors, and the plurality of inverter circuits are provided. In the inverter circuit, one of the inverter circuits to be detected is selected, and the one of the selected inverter circuits performs the detection operation to detect deterioration of the insulation resistance of the two or more motors. The method for detecting an insulation deterioration of a motor according to the fourth aspect of the invention, wherein the one or more inverter circuits are three or more inverter circuits provided for three or more motors, from the foregoing Determining a combination of two of the foregoing inverter circuits in an inverter circuit above the stage, and selecting two of the foregoing inverter circuits corresponding to the determined complex combination, respectively, and for the selected two inverters The circuit performs the above-described detecting operation to detect the parallel insulation resistance to ascertain the two inverter circuits including the inverter circuit that drives the motor having the parallel insulation resistance reduction, and the two inverters are respectively identified. The circuit performs the aforementioned detecting operation, and the motor having the reduced insulation resistance is ascertained based on the detected insulation resistance.